Purification of oils



Au 8, 1950 A. c. MGKINNIS PURIFICATION OF OILS Filed March 18, 1947 INVENTOR.

. $0 QEQMwRZb rroemsr Patented Aug. 8, 1950 i UNITED STATES, PATENT OFFICE PURIFICATION OF OILS Art C. McKinnis, Long Beach, Calif., assignor to 7 Union Oil Company of- California, Los Angeles,

Calif., a corporation of California Application March 18, 1947, Serial No. 735,492

looiaims.

This invention relates to the purification of oils by extraction and applies particularly to the removal from oil products of basically reacting constituents contained therein. This invention relates more specifically to the removal of basically reacting organic nitrogen compounds including heterocyclic monoand polynuclear compounds known as nitrogen bases from oils such as coal tar fractions, shale oil and shale oil fractions, mineral oil fractions and oil fractions obtained during the pyrolysis of protein material such as s cottonseed meal.

Crude petroleums, especially those produced in 7 California and South America, contain, beside hydrocarbons, small amounts of compounds of hydrogen, carbon, and nitrogen. The presence of these and other non-hydrocarbon compounds is often detrimental to the performance of the products prepared from petroleum and nearly 2.1-

ways their elimination from their particular Pctroleum fraction is desirable.

The nitrogen bases present in the shale oil and fractions thereof, petroleum fractions, coal tar. andoil fractions obtained from the pyrolysis of materials containing substantial amounts of" protein material, are heterocyclic monoand polynuclearorg'anic compounds of carbon, hy-

organic acids or by means of the relatively stron organic acids such as acetic, chloroacetic, oxalic acid or by acidic substanes such as picric acid,

etc., serve to remove from the oil a substantial portion of the nitrogen bases contained therein. It is also possible to separate nitrogen bases from a maJor portion of a diluting hydrocarbon oil by "extraction with a solvent in which the nitrogen bases are soluble but infwhich a larger part of the diluting hydrocarbon oil is insoluble. Such solvents which are applicable in such extractions include aniline, furfural, 'isopropyl alcohol and nitrobenzene. A more important and more widely used solvent is liquid surfur dioxide which is used to extract aromatic constituents together with the nitrogen bases from an oil in the socalled Edeleanu process (United States Patent No. 911,553, issued February- 2, 1909). The use of dilute acids, while simple in operation, involves the handling of relatively corrosive materials and results in the conversion of the cine base CmHzsN. In general this nitrogen base fraction present in the oils previously mentioned contains a large number of difierent compounds of carbon, hydrogen and nitrogen, which compounds have not been identified. These compounds react chemically similar to the aliphatic aminespfor ning stable water-soluble salts with strong acids;-

. Nitrogen bases have been removed from oils in a variety of manners. The repeated washing of the oil with a dilute strong mineral acid, such as sulfurous acid, sulfuric, nitric and other inacid extraction medium t a, salt when the nitrogen bases ,are liberated from solution. In many cases this salt which is formed is not readily reconvertible to the acid and consequently the reagent consumption is high. The liquid sulfur dioxide extraction method of the Edeleanu process requires use of low temperatures, high pressures and is more readily adaptable to the extraction of aromatics from oil fractions than to the specific preparation of nitrogen bases in concentrated form.

It has been discovered that acid ammonium or amino, or salts of strong non-volatile acids in an aqueous solution form excellent extracting solvents in a process which shows outstanding advantage over any previously used. The temperatures'and pressures of operation are very moderate, the economics of the process are good, and the solvents applicable to the extraction of nitrogen bases from oil fractions by the process of my invention are not particularly corrosive and may be conveniently handled in equipment iabrlcated from ordinarymetals of construction.

It is an object of my invention to provide a method for economical and efllcient removal of basically reacting constituents from oils.

A further object of my invention is to provide a method for the purification 'of-shale oil or petroleum oil distillates which permits the removal of nitrogen bases therefrom.

\ A further object of my invention is to provide a method for the separation of a highly concentrated fraction of such nitrogen bases from shale oil, petroleum oil, coal tar oils, or pyrolysis distiilates or fractions thereof.

It is a further object of my invention to provide a continuous process for the substantially complete extraction of such nitrogen bases from various oil with a minimum solvent or reagent loss.

Other objects and advantages of my invention will become apparent to those skilled in the'art as the description thereof proceeds.

Briefly stated my invention comprises a cyc1 i.

cal extraction process for the removal of nitrogen bases or other basically reacting constituents 'into neutralization vessel M which is equipped from either dilute solutions or.. ,concentrates.

thereof in which the extraction performed with an aqueous solvent containing an acidsalt of a relatively strong base and a strong npn volatile acid. In one modification of' my" inven-' portion thereof is evaporated from the aqueous solution containing the normal salt leavingan aqueous solution containing an acid salt. When the aqueous solution ofthe acid salt is contacted with an oil containing nitrogen bases, a soluble normal nitrogen base salt is formed which concentrates in theaqueous. extract phase. -.After separating the extract from the. nitrogen base.- free oil raflinate phase, combination withthe extract of that portion of thevolatile baseevaporated in the formation of the. aqueoussolution of the acid salt causes the nitrogen basesto. be liberated'from the extract by reformation of the normal salt. The free. nitrogen bases may be separated as a substantially pure phase vby decantation or other applicable procedure. The normal salt. employed in the aqueous solution is preferably such that evaporation .of a portion of the volatile base of the normal salt leaves a solution containing the acid salt which is capable of forming other normalsalts with nitrogen bases or other basic constituents of an oil. When the evaporated .baseis recombined with the aqueous solvent containing normal salts of the nitrogen bases, basically reacting constituents arereleased. More specifically .I employ as the extraction solvent, an aqueous solution. containing an acid salt of a strong non-volatile acid, which acid has one ionization constant of at least 1x10- and preferably between about 1 10- and about l 1 O The cation of theacid salt may include the ammonium ion or alkyl derivatives thereof as well as hydrogen. For-example, acid salts having an unneutralizedacid hydrogen which are included within the previous definition include an acid salt of arsenic, phosphoric, phosphorus, pyrophosphoric, sulfuric, and the like. These acids are'all strong non-volatile poly-basic inorganic acids. 4

Although in the preferred modification of my invention the ammonium acid salts are employed, others are applicable in certain instances such as the alkyl derivatives of ammonia which are the amines, such as mono-,'di-, and trimethylamine, or piperidine' which is also a relatively strong base. These compounds are. all low molecular weight saturated aliphatic amines which are relatively stronger bases than the nitrogen bases. present in hydrocarbon oils and-these compounds. are; Volatile bases. The preferred acid salts are the acid ammonium phosphates and sulfatessuch as ammonium dihydrogen phosphate, ammonium bisulfate with or without free acid.

The process and apparatus of my invention may be more readily understood by reference to the accompanying drawing which comprises a schematic flow diagram of one modification of the process of my invention. In the description of that modification of my invention which is illustrated in the accompanying figure, ammonia will be used as the cation of the salt used in the extracting solution. The acid may be any of those previously named, but for purposes of illustration will be considered to be phosphoric acid.

Referring more particularly to the accompanying figure, concentrated phosphoric acid is withline l2 controlled by valve l3 and is introduced with agitating means [5. Anhydrous ammonia, 20-

stored under its-vapor pressure in tank If; is withdrawn by means-of line I! controlled by valve l8 and is likewise introduced into neutralization vessel I l.

Water; if desired, may be added by means of line I9 controlled by valve 2:). The extraction process of my invention is recirculatoryin nature and results inasubstantially complete elimination of solvent or reagent loss. The amountsof acid and ammonia which are introduced into neutralization vessel 14 are quite-low and serve only-to make upC the :small amount of the salt which islost. The ratio-of thequantities of phosphoric acid and ammonia- .introduced into neutralizationves so] It is preferably controlled so as to producea normalsalt. For example, an aqueous solution of triammonium phosphate may be formed for subsequent heating and evaporation of a portion of ammonia therefrom forms anaqueous solution of an acid ammonium phosphate sa1twhich serves as an excellent extraction solvent. Be-' causeof the fact that heat is liberated in neutralization vessel Mduring the formation of the desired salt, cooling coil 2| is provided in order to maintain the temperature control over the contents of thevessel thus permitting-the-effective use of the heat of, neutralizationgenerated therein in the subsequent evaporation operation. -Theliquid'level-in vessel M is controlled by level controller 2-2 which 'actuates valve 23 which controls the flow through line 26. The aqueous salt solution is removed from vessel Mby means of line 2%, pump 25, line 26,-controlled by valve 23 and is combined with the recirculated reformed solvent recirculated through line 21. The recirculated solvent, together with the added solvent, is introduced by means of line 28 into solvent heater 29;: In solvent heater 29, the solventis'further heated to'a high temperature and is introduced by m'eans'of line 30 into vapor-liquid separating'drum 31 wherein the solvent is partially evaporated to form an acidic solution. A distillation tower ma be employed for evaporationofi .thesolvent. The product of evaporation, which include steam and certain amounts of the volatile cation 'of' the salt contained therein, are removed from drum 3| by means of line 32 controlled by valve 33 and are subsequently used as'more fully described hereinafter. The hot acidic solventcontained in drum 3| is remo'ved therefrom by means of line 34, and is passed through solvent cooler 35 wherein it is cooled to atemperature which is sufficiently low to permit efiicient extraction-- It is sometimes desirable to addvvater to the acidic. solvent, in which case it maybe. added by means of line 36. controlled by valve 31 into line 34. The cooled solvent is removed from solvent cooler35 by means of pump 38, line 39, line 4!), controlled by valve 4| which in turn is actuated by level control 42,- associated with drum 3|, and is introduced into the top of extractio'n tower 43. Y

The untreated oil to be extracted is removed fromtank 44 by means of line 45 controlled by valve 46 and is introduced into the lower portion of extraction tower 43'. Extraction tower 43 may conveniently comprise a packed column of suitable diameter and suitable height depending upon the type of solvent used'and the type of oil to be treated. The oil rises upward through column 43 as the continuous phase and the solvent introduced into the top of tower 43 flows downwardly as thediscontinuous phase, countercurrent to the rising oil. The rafiinate, or treated oil from which the nitrogen bases have been substantially completely removed, is removed from the top of tower by means of line 41 and isaccumulated in tank 48. The solvent dissolves the nitrogen bases from the rising oil and forms'soluble salts therewith which are carried downward through tower 43 with the discontinuous solvent phase. Theaqueous solvent phase containing the nitrogen bases as dissolved salts and forming the extract accumulates in the bottom of tower 43' and is immiscible with the oilrising therethrough.

The position of the interface between the oil or raflinate phase and the'solvent or extract phase in the bottom of tower 43is controlled-by differential level controller 49 which'actuates valve 50 which in turn controls the rate at which the extract is removed from tower 43 through line 5| under positive suction induced by pump 52. The extract thus removed is conducted by means of line '53 controlled by valve 50 and is introduced with agitating means 55,

In the particular modification of my invention into neutralization vessel 54 which is equipped as herein described, ammonia vaportogether with The immiscible liquid phases are removed from neutralization vessel 54 by means of line 55 controlled by valve 58 and are introduced into separrator 59 where, in the particular modification being described, the oily nitrogen base phase set-' tle sto the top while the regeneratedsolvent phase settles to the bottom. The supernatant oil phase containing the nitrogen bases is removed from separator 59 by means of'line 60 controlled by valve GI and is introduced into tank 62 which is provided for the accumulation of separated nitrogen bases. The regenerated solvent, which issubstantially completely free, of nitrogen bases, is removed fromseparator 59 by means of line 63 and is pumped by means of pump through line 21-controlled by valv '65 and is introduced into line 28"wherein it is combined with a small amount of added solvent, and is through'the system.

As previously described, cations other than ammonia may be employed in the salt used in the recirculated.

aqueous solvent and the choice of such a cation which is most suitable for a given application in the separation of nitrogen bases from oils gov erns, to a large extent, the type of equipment used in separator 59 in which the extract is freed of nitrogen bases. For example, in the treating of oils having low boiling ranges, and in which are contained nitrogen bases such as pyridine and its low molecular weighthomologs, the equipment necessary in separator 59 to efiiciently separate the nitrogen bases from the extract obtained from the bottom of tower 43 comprises an extraction tower whereby the primary extract obtained from tower 43 may be contacted with a ,ture of about 100 F. with'an aqueous soluper cent nitrogen bases. a from the bottom of the tower and heated to a low molecular weight organic solventsuch as for example, petroleum ether, benzene, or other applicable molecular weight nitrogen bases ma be efficiently removed. A secondary extract is thereby .ob-

tained containing the nitrogen bases which may,

be separated by distillation. The water soluble nitrogen bases may be removed in some cases by distillation of the primary extract In another possible modification of my invention, ammonia or added basic constituents such as the low molecular weight amines and similar to separate therefrom a portion of the nitrogenbases which may then be separated from the regenerated solvent most conveniently by heat-. ing and subsequent decantation, or by further extraction. The regenerated solvent thus obtained is not completely free from, dissolved nitrogen bases and is recirculated from separator as through line 53 under positive suction induced by pump 64, through line 21 to heater 29 where it is further heated to a temperature which is sufficiently high to substantially completely evap-- crate the remaining nitrogen base contained therein. Subsequent cycles of this modification of the process conform substantially to that described except that in this modification the nitrogen base rather than the ammonia is the cation;

of the salt used in the extracting solvent.

The following examples will serve to more clearly illustrate my invention:

Example I A gas-oilfraction prepared. from oil shale by; high temperature oil shaleedu ction and sub, sequent fractional distillation has the following.

characteristics: v

Boiling range, 425 to 560 F; Gravity, 32.2" AQP. I- Nitrogen bases, 7.7 volume per cent The nitrogen bases contained in this gas-oil fraction comprise the substituted quinoline type of nitrogen compound, This gas-oil fraction is,

treated at atmospheric pressure at a temperae tion of 25 weight per cent ammonium bisulphate (NHHso) in a packed tower. The raffinate' rises throughthe tower as a continuous oil phase and is removed containing less than 0.2 volume The extract is removed immiscible solvent, whereby the low- In carrying out this modificatemperaturerbetweenrabout 2.00? F. and 3009-1 causingzthereby a; substantially complete separation! from :thewextract of the nitrogen bases as aiseparate oil layer. The'twophases are separated byrmeans :of: decantation and; the solvent phase xcontainingw a small. amount of dissolved nitrogen base, is-cooledwand' returned-as freshsolvent to the extraction tower.

J Example II Phei"sliale oil' gasoline'prepared from the same shaleioil scurcaasl'the gas-oil described in Example: I has: the following. properties:

Boiling.range,-280.to 405.? F. Gravity lfifl? A. R. I. Nitrogen bases,..3.2 volumepencent The nitrogen "bases presentin this gasoline appear to -be alkylated pyridines and because the lowermolecul'ar weight alkylated pyridine-s are soluble-in water andaqueous extraction solutionsj-theymust'be' separated in a different manner from the nitrogen bases present in the gasoil fraction. A 15 weight per cent solution of triammonium" phosphateis heated and water and ammonia are evaporated leaving anacid solution of ammonium dihydrogen-phos'phateand phosphoric acid. This acid salt soiution is'cooled to'1'0O--F. and used to extract the shale oil-j gasoline-in a packed tower. A=-rafiinate isproduced from the top-f the tower which contains less than 0.2volume percent nitrogen bases; An extract containing the-nitrogen bases as' the'normal ammonium nitrogenbase-'phosphate'salts is removed from the'tower-bottom.-' The extract is contacted with the-previonsly-- evaporated ammonia and water reforming the normal triammonium phosphate salt and substantially completely liberating the nitrogen bases. The normal salt solution containing' free nitrogen bases partly in solution is extracted in a secondary extraction tower with a" low boiling-hydrocarbon solvent thereby separating the nitrogen bases as a secondary extract.

Thesecondary raflinate consisting'oi the re-' formed-normal salt solution, is-returnedto the evaporationapparatus for evaporation of ammonia andconversiontothe acid salt. The secondary extract-consisting of the nitrogen bases in a low boiling-hydrocarbon solution is distilled to efiect a complete separation.

The gas-oil fraction-described in Example I was treated as follows with an ammonium phosphate extracting-solution." Theextraoting solvent utilized comprises a 25 weight per cent solution of triammon-ium phosphate. This extraction solution is heated and suficient' quantities of ammonia and watervapor ,are. evaporated .so that the composition-of the:salt in the solvent approximates that of the ammonium dihydrogen: phosphate solution as in Example II with excess phosphoric, acid. This acidic solvent isusedas theextracting; solution in an, extraction. tower wherein it..countercurrently contacts'the, gas-oil fractionand produces a raflinate containing less than.0;l5.volume percent nitrogenbases andan. extract. which-contains the. nitrogen bases as normahammonium..nitrogen base phosphate salts. Theextractis removed from the. extractiontower and'nombin'ed with the ammonia evaporatedfrom thesoriginal. triammonium phosphate solutibncausing. the substantially .comp1etesepa--.

ration .of= the: nitrogen rbases? into. an :oily. iphase. Thewoilyphase containing: the separated substituted quinolineaandasheavier nitrogen bases is separated.- by. :decantation .from: thereformed aqueouss-isolutiom -.of triammonium. phosphate which contains a small amount of acombined'nitrogenrbase. z Therreformed solutionis-recycled to P the euaporatiomgapparatus for .reuse in the extraction tower;

\ The methods of: invention as .herein: disclosed for; the .--removalof: nitrogen bases in particular: and other basically reacting I compounds in: general. from cilsi apply equally well .to the dilute-solutions; lot-such basically reacting materials .or concentrates. .thereoi. and. the use of dilute: SOlHliiOllSwi-l'l the-examples or. the mode of preparation or the source-tot: the oil containing such nitrogen-bases mustnot-be taken aszlimiting my invention. As previously stated in: this specification,,zphosphoricwacid, lsulfuricoacid, arsenic acid and; other mom-volatile acidswhich. have ionization l constants within. the limits previously set..forthare. applicable. tOzlihfiwOll purification processes herein: disolosed, -.and my. invention is not. tobe limited: to. the particular acids used in the; :examples or. in r the description. Similarly, the, specific: concentrations of; salts indicated in thelexamples-zof applicable. solvents are only illustrative of: the. process :of my invention andsalt concentrations..ofifronrasz-lowias 1%- to 2-%-by weight .to-as; high (on higher-than about 40%"by weight. arezapplicablea depending: ,upon the salt used. the temperaturepf operation-,; and. the =type of .oil being:treated..-- Althoughamoperating pressure-was-not. indicatedin the description of my invention. it-.ismost convenient .to carry out the process at -pressurestsubstamtially equal to atmospheric pressure although in some instances it is advisable to utilize elevated pressures such. as when solvents of low boilingirange are employed in t'he secondary extraction: indicated: or other particularacases.

Having described and illustrated my invention for the removalfofrbasically reacting constituents from oils-"by extraction withaqueous-solutions of acid salts -"andrealizihg that many modifications thereof may*'occur-tdthoseskilled in the art without departing' from the spirit and scope of my invention,

I claim:

' l. A continuous process for the separation of nitrogen bases from hydrocarbon oil solutions thereof which" comprises combining a volatile base selectedfrom the classof volatile bases consistingofammoni'a and'the. mono-; di-. and tri= methyl amines and a strong non-volatile polybasic'inorga-nic ac'idtinthe presence of water to form-an aqueous solution of the normal salt of said; volatile" base and said. non-volatile. acid, heatingsaid aqueous solution and. evaporating thereby a portion. of said volatile base-to form an.

aqueous sol'utiom'of an. acid salt of said. volatile base and said. non-volatile. acid, contacting said hydrocarbon 'oil solution Joflnitrogen bases with said aqueous solution oi said. acid salt .to iorm a hydrocarbon oilrfiinate andan. extract containing. said nitrogen bases as. normal nitrogen base salts,,.separating. said raifinate from said. extract, coinhihing. said extractwith the evaporated portion of said. volatile .basethereby reforming. in: solution said normal salt and. liberating said. nitrogen bases, removing the liberated nitrogen bases and returningthesolution of. normal salt fonreuse in theprocess.

-- =2'.=-A continuous process for the separation of acid ammonium salt to form an extract containing said nitrogen bases as normal ammonium nitrogen base salts of said non-volatile acid and a rafiinate which is substantially completely free of said nitrogen bases, separating said extract from said rafiinate, combining said extract with the ammonia evaporated in the formation of said aqueous solution of said acid ammonium salt thereby reforming said aqueous solution of said normal ammonium salts and simultaneously liberating said nitrogen bases from said normal ammonium nitrogen base salts in said extract, separating the liberated nitrogen bases in substantially pure form from the reformed aqueous solution of said normal ammonium salts, and returning said solution of normal salts for reuse in the process.

3. A continuous process for the separation of nitrogen bases from hydrocarbon oil solutions thereof which comprises combining ammonia with sulfuric acid in the presence of water to form an aqueous solution containing less than about 40 weight per cent of diammonium sulfate, heating said aqueous solution and evaporating therefrom a portion of said ammonia to form an aqueous solution containing ammonium bisulfate together with free sulfuric acid, contacting said hydrocarbon oil solution of said nitrogen bases with said acid ammonium bisulfate solution to form an extract containing said nitrogen bases as the normal ammonium nitrogen base sulfate salts thereof and a rafiinate which is substantially completely free of nitrogen bases, separating said raffinate from said extract, combining said extract with the ammonia evaporated in the formation of said acid ammonium bisulfate solution thereby liberating from said extract said nitrogen bases as an insoluble phase and simulta neously reforming said aqueous solution containing said diammonium sulfate, separating by decantation the liberated nitrogen bases in substantially pure form, and returning the reformed aqueous solution of diammonium sulfate for reuse in the process.

4. A continuous process for the separation of nitrogen bases from hydrocarbon oil solutions thereof which comprises combining ammonia with phosphoric acid in the presence of water to form an aqueous solution containing less than about 40 weight per cent of triammonium phosphate dissolved therein, heating said aqueous solution and evaporating ammonia therefrom thereby forming an aqueous solution containing am monium dihydrogen phosphate together with free phosphoric acid, contacting said hydrocarbon oil solution of nitrogen bases with said last-named aqueous solution to form a rafiinate substantially completely free of nitrogen bases and an extract containing said nitrogen bases as the normal ammonium nitrogen base phosphate salts thereof, separating said extract from said raflinate, com bining said extract with said ammonia evaporated "in the formation of said last-named aqueoussolution' thereby liberating said nitrogen bases from said extract and simultaneously ref orming'said aqueous solution containing said triammonium phosphate dissolved therein,'fractionating said solution of liberatednitrogen bases andreformed aqueous triammoniumphosphate solution, separating thereby a first fraction containing said nitrogen bases in substantially pure form and a second fraction containing regenerated triammonium phosphate solution, and returning said second fraction for reuse in the processf I l 5. A continuous process for the separat'ion of nitrogen bases from hydrocarbon oil which comprises heating an aqueous solution of a normal salt of a strong non-volatile polybasic inorganic acid and a volatile base selected from the class consisting of ammonia and the mono-, diand trimethyl amines thereby evaporating a portion of said volatile base to form an aqueous solution of an acid salt of said non-volatile acid and said volatile base, contacting said hydrocarbon oil containing nitrogen base with said last-named aqueous solution to form a hydrocarbon oil ramnate substantially free from nitrogen bases and an extract containing said nitrogen bases as normal nitrogen base-volatile base salts, separating said raflinate from said extract, combining said extract with the evaporated portion of said volatile base thereby reforming said normal salt and liberating said nitrogen bases, removing the liberated nitrogen bases and returning the solution of normal salt for reus in the process.

6. A continuous process for the separation of nitrogen bases from hydrocarbon oil which comprises heating an aqueous solution containing less than about 40 weight per cent of diammonium sulfate and evaporating therefrom a portion of said ammonia to iorm an aqueous solution containing ammonium bisulfate together with free sulfuric acid, contacting said hydrocarbon oil containing nitrogen bases with said acid ammonium blsulfate solution to form an extract containing nitrogen bases in the form of normal ammonium nitrogen base sulfat salts and a hydrocarbon oil raiiinate which is suostant1ally free of nitrogen bases, separating said rafiinate from said extract, combining said extract from the ammonia evaporated in the formation of said acid ammonium bisulfate solution thereby liberating from said extract said nitrogen bases and simultaneously relorming an aqueous solution of diammonium sulfate, separating the liberated nitrogen bases in substantially pure form and returning the reformed aqueous solution of diammonium sulfate for reuse in the process.

'7. A continuous process for the separation of nitrogen bases from hydrocarbon oil which comprises heating an aqueous solution containing less than about 40 weight per cent of triammonium phosphate and evaporating ammonia therefrom, thereby forming an aqueous solution containing ammonium dihydrogen phosphate, contacting said hydrocarbon oil containing nitrogen bases with said last-named aqueous solution to form a raflinate substantially free of nitrogen bases and an extract containing said nitrogen bases in the form of the normal ammonium nitrogen base phosphate salts thereof, separating said extract from said rafiinate, combining said extract with the ammonia evaporated in the formation of said last-named aqueous solution thereby liberating said nitrogen bases from said extract and simultaneously reforming said aqueous solution of tri- 

1. A CONTINUOUS PROCESS FOR THE SEPARATION OF NITROGEN BASES FROM HYDROCARBON OIL SOLUTIONS THEREOF WHICH COMPRISES COMBINING A VOLATILE BASE SELECTED FROM THE CLASS OF VOLATILE BASES CONSISTING OF AMMONIA AND THE MONO-, DI- AND TRIMETHYL AMINES AND A STRONG NON-VOLATILE POLYBASIC INORGANIC ACID IN THE PRESENCE OF WATER TO FORM AN AQUEOUS SOLUTIN OF THE NORMAL SALT OF SAID VOLATILE BASE AND SAID NON-VOLATILE ACID, HEATING SAID AQUEOUS SOLUTION AND EVAPORATING THEREBY A PORTION OF SAID VOLATILE BASE TO FORM AN AQUEOUS SOLUTION OF AN ACID SALT OF SAID VOLATILE BASE AND SAID NON-VOLATILE ACID, CONTACTING SAID HYDROCARBON OIL SOLTION OF NITROGEN BASES WITH SAID AQUEOUS SOLUTION OF SAID ACID SALT TO FORM A HYDROCARBON OIL RAFFINATE AND AN EXTRACT CONTAINING SAID NITROGEN BASES AS NORMAL NITROGEN BASE SALTS, SEPARATING SAID RAFFINATE FROM SAID EXTRACT, COMBINING SAID EXTRACT WITH THE EVAPORATED PORTION OF SAID VOLATILE BASE THEREBY REFORMING IN SOLUTION SAID NORMAL SALT AND LIBERATING SAID NITROGEN BASES, REMOVING THE LIBERATED NITROGEN BASES AND RETURNING THE SOLUTION OF NORMAL SALT FOR REUSE IN THE PROCESS. 